What do you build today for a new quarter of around 4,000 residents if you do not know what gas, power and hydrogen will cost in fifteen years? N-ERGIE's answer for the Tiefes Feld neighbourhood in south-west Nuremberg is a bit of everything. In a project update dated 3 November, the main contractor Kraftanlagen Energies & Services reported that most of the floor slabs are finished, the first exterior walls are up and the job is on schedule for commissioning in 2028.
The plant as the contractor describes it:
- two combined heat and power units, each with 4.5 MW electrical and 4.4 MW thermal output, prepared for a later switch to hydrogen
- a large heat pump made of four modules that use ambient air
- a 60 MWh thermal store, built as a pressurised tank for up to 115 °C
- existing electric heaters from N-ERGIE's Sandreuth cogeneration plant
The contract was signed in March 2026 and ground was broken in June. Kraftanlagen is responsible for design and construction, including the process and electrical systems and the ancillary plant. The update gives neither the investment nor the capacity of the heat pump, and it does not say which fuel the engines will start on.
Four heat sources on one network
The logic is easy to follow. When power prices are high the engines run, sell electricity and fill the store; when prices are low the heat pump and the electric heaters take over. The store is what lets each machine run when it earns money and not merely when the neighbourhood happens to be cold.
The engineering is in the temperatures. An air-source heat pump is happiest delivering moderately warm water, engine heat comes hotter, and the store is rated to 115 °C. Getting all of that onto one network without mixing away the hot end usually means staging - the heat pump lifting the return first, the hotter sources topping up - and a store that stays stratified.
On the engine side the circuits are the familiar ones from any engine power plant: jacket water, lube oil and charge air each give up heat through their own exchangers, and the district heating water is kept apart from the engine coolant. Hydrogen readiness changes little there. It changes the gas train and the engine, not the plate pack.
One practical point for a plant with this many modes: the heat exchangers between engine and network see very different loads over a year, from full output in a cold spell to long standstill in summer. Standstill is when deposits settle. A flushing routine in the operating manual is cheap insurance.
Sources: Kraftanlagen Energies & Services
